(a) Field of the Invention
The present invention relates to a reverse-stop mechanism of a curtain, and more particularly to an application to a vertical or horizontal type curtain that stops transmitting a reverse force, caused by gravitation or an external force, and also outputs varied powers through differential speeds formed by different pitch circle diameters of gears.
(b) Description of the Prior Art
Referring to FIG. 1. To enable a reverse-stop mechanism, a drive assembly 12 is formed in a conventional curtain 1.
Referring to FIG. 2. The drive assembly 12 is driven by operating a bead-chain 121 to rotate a chain wheel 126, which enabling a worm 125 to drive a worm wheel 124. Besides manual operation to provide a rotation force, an electric motor can be used to replace the chain wheel 126.
Referring to FIGS. 1 and 2. Through a transmission stick 122, the drive assembly 12 drives wire-collecting tubes 123, which wind up or down curtain sheets 14 through wires 141. Adjustment of angles of curtain sheets 14 is made by overturn plates 13 to move wires 142.
When blowing by wind, the curtain sheet 14 may slip downwards, transmitting a power through wire-collecting tubes 123 and the transmission stick 122 to slip the drive assembly 12.
The structure shown in FIG. 2 can be a better design till now. While the worm wheel 124, being formed inside the upper horizontal block 11, is slim and small and while the engaging force on the worm wheel 124 is limited to a face of a cog, damages can easily occur on the cog of the worm wheel 124 or the worm 125, thereby causing a slip and even losing locking capability.
The drive assembly 12 can also be applied to a cloth-curtain, which suffers similar wind pressure and self-weight effect, thereby necessitating a reverse-stop function to stop slipping.
Referring to FIGS. 3 and 3A. A horizontal type curtain includes a wire 140, an adjustment stick 120, and an upper horizontal block 11 connecting with a curtain sheet 14, which can be wound up or down by operating the wire 140. By operating the adjustment stick 120 to rotate a worm 125, a worm wheel 124, and a transmission stick 122, an angle of the curtain sheet 14 thereby being adjusted. With the worm 125 gearing the worm wheel 124, the transmission stick 122 thereby being able to resist an external or a self-weight force.
While the curtain can be as high as 30 meters, the adjustment stick 120 can't be that long, due to a packing size constraint, thereby, instead of using the adjustment stick 120, a chain wheel is used.
Referring to FIG. 4. As far as the chain wheel is concerned, a conventional design is to operate a bead-chain 121 to rotate a chain wheel 126 and other drive elements in a direction of the transmission stick 122 through a planet gear set 18. Driving by the chain wheel 126, a sun gear 181 will rotate to drive a planet gear 182 rotating round a fixed annular gear 183, which rotates a wheel disk 180 to drive a shaft 190 connecting to a main thrust shaft 191 through a stop spring 192, thereby enabling the main thrust shaft 191 to drive the transmission stick 122. The stop spring 192 can be de-compressed, when a force from the shaft 190, or compressed to stop transmitting a rotation when a force from the main thrust shaft 191, thereby forming a reverse-stop function.
The stop spring 192 is locked on an end and the de-compression is achieved when a shrinking of the diameter of the spring 192 is made by an external twisting force from the main thrust shaft 191. The design of the stop spring 192 is common in conventional curtains, thereby no further discussion regarding this subject.
The design in FIG. 4 can also be applied to drive structures in FIG. 1 such that by pulling the bead-chain 121 to enable the curtain sheet to wind up or down and also adjust incoming light angles.
With a force by pulling the bead-chain 121 or by wind pressure or self-weight effect in an opposite direction, the stop spring 192 will be de-compressed or compressed, thereby enabling the curtain being wound up or down or adjusted for different light incoming angles or enabling a reverse-stop mechanism. While the compression force and the outer perimeter of the shaft 190 exceeds limits, slipping and losing the reverse-stop capability can be happened.
Referring to FIG. 5. A conventional vertical type curtain includes a drive assembly 12, driven manually by a wire 16, formed on an upper horizontal block 11, wherein curtain sheets 14 suspended through suspension shafts 15.
Referring to FIG. 6. Curtain sheets 14 can be operated through a suspension shaft 15 connecting with a bevel wedge gear 17, to be driven by the drive assembly 12 in order to rotate a transmission stick 171.
When driven by the drive assembly 12, the bevel wedge gear 17 rotates suspension shafts 15 to alter different incoming light angles of curtain sheets. To prevent a wind pressure from causing a reverse driven force transmitting to the drive assembly 12, a structure similar to that in FIG. 2 is formed. As a result, cogs of the worm gear can be damaged, causing a slip and losing reverse-stop capability.
In recent years, other reverse-stop designs were developed, such as using an electromagnetic control switch or other electric automatic devices. As a result, defects can be relaying upon a power supply and also complex in structure.